| Boiling Point No. 07 - December 1984 |
We have received 4 publications, and one unpublished article from Nepal, 2 of the publications are on installation of improved pottery insert stoves, 2 of the reviews are on stoves for large sized cooking pots and the final review is a survey of pottery insert stove in Khopasi. Also included in this edition is a leaflet on a Rice Husk burning stove in Thailand, a summarized report on new stoves in Niamey and an article on designing multi-pot mud stoves from India.
Clearly the wood fuel problem and the need for better, safer and more fuel efficient stoves are being taken very seriously by the Nepalese Government and the associated agencies such as the Community Forestry Division, RECAST, World Bank, UNDP, FAO, and UNICEF. Not only have they done valuable stove development and testing work on stoves to suit the rather specialized climate and housing conditions of the region but they have also produced these publications for the guidance of field workers and stove builders to help the process of introducing better stoves.
The first "Manual on the Installation of Improved Insert Stoves in Nepal from the Community Forestry Development Project is designed for use on training courses as well as for general field work. It is comprehensive, 62 pages in English and Nepali on alternate pages, practical rather than technical; profusely illustrated with line drawings showing every stage of construction of 2 pot ceramic liner, mud and brick stoves with chimneys and their installation in a house. It also explains the advantages of this type of stove and how it should be used and maintained.
The second "Less Smokey Rooms" by A. Bachmann for UNICEF has 44 pages in English with good diagrams and not so good reproductions of photographs. It deals with the making, installation and safety of different types of wood burning cooking stoves suitable for Nepal and Bhutan, made of bricks, mud and cast iron. They are chimney stoves with 1, 2 or 3 pot holes for cooking and some have jackets for water heating. There are also simple, sheet steel stoves for room heating.
The instructions are for the installation of cooking stoves in masonry houses (1 or 2 storey) or houses with brick chimneys, They show how to design and make chimneys of masonry or sheet metal and how to install them safely. There is also useful advice on safety, fuel economy, cooking and room heating and insulation.
The third publication (20 pages) also from UNICEF by A. Bachmann and T.D. Kongtsa "A Cooking Place for Terse Sized Pots" is a construction manual for stoves for wood dyeing and cheese making for which traditional stoves are usually smoky, unsafe and waste fuel. The stoves are wood burning and are designed to suit particular pots typically about 80-9Ocm in diameter. They are made of bricks with sheet steel or brick chimneys with dampers and there are diagrams giving critical dimensions.
We have received an unpublished test report by Mr K. Sulpya from the Research Centre for Applied Sciences and Technology, Kiritipur, Nepal, which also describes a wood burning, single pot, community stove made from bricks and mud and sheet steel but without a chimney. Besides cocking large amounts of food it can be used for dyeing purposes in cottage industries. The test results given using 50 litres of water show considerable savings over the "traditional fireplaces".
RECAST COMMUNITY STOVE: SUMMARY OF TEST RESULTS
wt wood used (kg)
wt water evap (kg)
time to boil
The results are based on an average of 3 boiling water tests for each stove with a 30 minute simmering period (BP + 30). The wood used was a traditional hardwood (sal) with a moisture content of 10% dry weight basis. The diameter of the cooking pot was 55 cm and 50 cm in depth. Fifty litres of water were brought to the boil and simmered with a lid. 18 gms of kerosene was used as kindling.
The RECAST single pot stove limits the size of the firebox chamber, while the provision of secondary air holes helps in better combustion. The pot sinks into the firebox chamber which helps in reducing heat losses from the pot sides.
The final publication 'Survey of New Stove Use in Khopasi' by K. Basnet and produced by the Small Farm Family Programme of ADB Nepal and UNICEF 1983 is 16 pages long. The purpose of the survey was to ascertain the level of acceptance of 112 stoves distributed in 6 villages and the problems encountered and so to help with stove improvements. In general, the stoves were found to be suitable, well promoted and installed and well accepted.
The report is clear and simple to read but lacks a brief description of the Modified Magan Chulo and evidence to support the validity of the findings based on users' opinions.
112 stoves were distributed but only 71 installed, (mainly for lack of technicians) over a period of 15 months. Over 90% were said to be in good condition and few had cracks; 14% were badly located in the kitchens; 90% were a good fit with the pots except for the large pots, used for brandy or animal feed for which the stove was not designed and 90% of the 71 stoves were being used daily for most cooking.
Fuelwood saving is given as 36.22% ie 13.76 kg/stove/week worth Rs4 compared with stove cost of Rs80 ie 20 weeks pay back. Stove life is not yet determined. The report -does not- say - how the percentage saving was measured, except perhaps from the user's estimates of consumption. Questions were asked about cooking times, convenience, smoke and fuels used but the answers are not reported.
This report recommends improved chimney cowls to prevent smoke blow back and metal pot seats for fitting small pots. More durable mud coverings are also recommended.
Population and Community Development Association (PCDA) - Thailand and the Royal Thai Forestry Department (RFTD).
The Thai PCDA has produced a 5 page leaflet on how to make the Meechai rice husk burning stove (see Fig. 1). The stove was initially found in Kampuchea and was brought to Thailand by Thai extension workers of the PCDA who saw the stoves, made from scrap steel, being used by refugees in the Kao-I-Dang refugee camp. The PCDA promoted the stove in Thailand and named it the "MEECHAI" stove after their well known and charismatic director Mr Meechai Velravaitaya.
The RFTD improved the design, added the thermal insulation and thousands of these stoves have now been made in Thailand.
The stove is reported to have an efficiency of 16-19% at a power output of 9kW in no wind, and to boil 3.7 kg of water in 12 minutes in a 24 cm diameter pot. There is no indication of user reactions. In areas where there is a good supply of cheap rice husks it may fill an important need. There are some good points in the design and it would be interesting to see further test results and to know more of reactions from users and makers.
As will be seen from the diagram, the outer case and -combustion- chamber is a perforated sheet steel cone (0.7 mm thick) sitting in a steel tripod and holding the burning husks -and supporting the stave body. This is a 2.5 cm thick ceramic cylinder in a sheet steel case resting on 3 or 4 brackets fixed to the inside of the cone. The cooking pot sits on the top of this cylinder. The -rice husks are fed into the cone from above; and around and the outside of the cylinder, into the 2-2.5 cm gap. The cone angle of about 60 degrees is designed to allow the rice husks to slide down as they are burnt away at the bottom. Ash collects an the moveable disc under the bottom of the cone. The e position of this disc and the ash removal are the only controls to adjust air for combustion, so the burning rate will depend mainly on the rate of feeding in the fuel. Attention is needed every few minutes.
The flames and hot gases should came up inside the ceramic cylinder, pass over the pot bottom and out through the 3 cutaways in the top of the cylinder. The stove will take almost any type of pot or wok, and is portable, but the fuel efficiency is limited because the pot does not sit into the stove to receive radiant heat through its sides, nor is it protected from cooling winds.
The stove is said to cost $7.50 in Thailand and as there is no grate to burn through it should have a reasonable lifetime, particularly if it has an insulating liner of clay and rice husk ash. Two to three years is claimed. It is not difficult to make, and if welding is not available, the joints can be folded or rivetted. The perforations can be made by hammering a large nail through the cone from the inside surface.
As wood fuel and charcoal become scarcer and dearer there will be more need for efficient rice husk stoves to suit different cooking systems. The progress of the Meechai Stave should be followed to see if it has the potential for development and wider promotion.
GILLES DE CHAMBRE
Association Francaise des Volontaires du Progres
Republic of Niger
Ministry of Mines & Industry
National Committee for Improved Stoves
This is a 13 page report with tabulated results from 2 series of field trials, each of 2 weeks duration. The test report form is the one specified at the Arlington, USA meeting in December 1982.
The tests showed a wood saving of more than 30% compared with the traditional "Malgache" stove which was shown to have a PHU of 21% compared with 14% for 3 stones.The new stove was considered to be ready for large scale dissemination which is now beginning to take place in Niamey.
A detailed plan drawing and overall dimensions of the stove were not presented in the report.
SUMMARY OF REPORT
LE FOYER 'MAI SAUKI'
The stove tested was modified from an improved Burkina Faso design to suit Niger conditions eg to be made without welding. Preliminary field tests were inconclusive but encouraging, and lab tests showed savings of 30%, so two more comprehensive test series were carried out and the results of these follow.
Further work was done on the stove design for simplicity and improved performance based on experience in other Sahelian countries and on local manufacturing skills and a critical dimension was found to be the space between the pot wall and the stove wall (0.5-0.7cm) Lab tests in Niamey gave a PHU of 32%.
The traditional "Malgache" stove has been built and improved in Boukaki for more than 10 years and costs 250CFA. It has given a PHU of 21% compared with 14% for 3 stones as the fire is protected from the wind and the distance from fire to pot bottoms is controlled. 50 stoves were measured and found to have little variation despite being made of reclaimed sheet. This showed that the artisans were capable of making stoves accurately.
For good cooking the pot must match the stove and so the pots in use were measured and found to vary slightly within each size eg 86-89cm circumference. However these variations can be accommodated by a range of stoves.
FIELD TESTS (JAN-MARCH '84)
The 36 test households selected formed one complete street in Niamey, occupied by low income renters who need to economise on fuel, close together to facilitate surveying and well known by the testing technician. All families in the street were included irrespective of size. The first week they measured wood fuel consumption with the traditional stove and the second with the improved stoves - 2 weeks were allowed in between for the women to learn to use the new stoves.
The 3 surveyors weighed each family's wood each morning and filled in forms and tried to ensure that no other wood was used. The women were advised on how to use the stoves efficiently, both before and during the test weeks.
The table of results showed for each week and for each household, the number of persons and the average weight consumed per person per day. The last column showed the percentage decrease or increase. In the first test series, 2 households were eliminated because of absence for part of a week, and because the results were not reliable and the consumption was considered to be extreme.
Average overall savings in the first series were 30% with an individual range of 22% increase to 66% reduction. These wide variations were attributed mainly to information inaccuracies. The high figures were attributed to specially careful use of fuel by women who had to pay for the wood themselves. Other women who received a daily 100CFA of wood were less careful. In some families the increased efficiency resulted in greater use of the stoves - eg for hot water as the tests were conducted in the cool season. Such variations are said to disfavour the new stoves as the large vessels used would not suit the type of stove. There was some correlation between the family size and the wood consumption but this did not account for all the variations and several other factors are given.
The results of this first test series were considered very satisfactory showing that the laboratory indicated potential improvement of 30% had been achieved. However, there was doubt as to how much of the improvement was due to the stove itself and how much to the operating instructions provided. A second field trial was therefore held without any instruction and allowing only 5 days for the women to get used to the new stoves.
The procedure was otherwise the same except that the number of families was reduced to 31 because of the absence of one survey technician and the choice of a different locality in Niamey. These households had a higher living standard.
The average saving was 34% and the difference from the first series was attributed to warmer weather - less water heating in the morning and absence of training for the women: It was not possible to estimate the balance between these 2 factors but it was concluded that intensive or organized training in new stove use is not necessary.
1) The stove is now ready for large-scale promotion, because:
- it provides 30% saving in the field; - it is well adapted to local cooking and does not require changes in the women's cooking habits;
- after two and a half-months of use in the first' area tested, all the stoves are still in use;
- 50 more stoves have been sold to - women in the area.
The main disadvantage is the need for several sets of templates for different sizes of stoves to suit different pots.
2) For a family of 6 people the cost of 2 new stoves (1,500CFA) will be repaid by fuel cost savings in 30 days. The daily saving from one new stove would be 50CFA. For a stove life of only 1 year 16, 250CFA would be saved and for 2 years 34,500CFA.
3) Initially, a stove promotion team will be needed to teach the women to choose a stove to suit each ' pot otherwise they tend to choose too large a stove.
Design of Multi-Pot Mudstoves - A Modular Approach by Manmohan Singh Sodhi
This short article, which will soon be published in the Appropriate Technology Journal, describes a useful method of simplifying the process of improving the design and performance of multi-pot mudstoves. It could be used by any project making a serious attempt to improve a stove design and would save a considerable amount of time, labour and material in making and testing, as well as reducing the confusion and frustration which threatens anyone experimenting with a large number of variable parameters.
It is simply a matter of making the mud stove in 3 or 4 separate 'modules', eg, combustion chamber, second pot seat and passages, outlet passages and damper, chimney. The parts are joined together for testing and then any part can be removed, its supposedly critical elements modified and replaced for comparative tests without altering the rest of the stove in any way. The author claims that savings of 50-70% in fuel consumption can be obtained by the progressive use of this method for all the stove modules.